A host of methods have been described in the scientific literature and the patent literature, for imaging through diffusing media. However, there remains a need to accomplish just the opposite: to project images or other wave fields into a space that is obscured from the projector by a diffusing medium.
Recent work in microscopy has shown that it is possible to pre-distort an optical wavefront in such a way that a diffuser restructures the wavefront to form a converging spherical wavefront that focuses to a point. For example, I. M. Vallekoop et. al., in “Exploiting disorder for perfect focusing” (ArXiv:0910.0873v1 [Physics.optics] 5 Oct. 2009), which is hereby incorporated by reference in its entirety, describe using a spatial light modulator to pre-distort a wavefront and, via a learning algorithm, transmit the wavefront through a very strong diffuser, to a finely focused spot.
A substantial amount of work has been done to employ arrays of projectors to form so-called “light field displays”, which essentially reverse the process of lenticular photography. For example, Fellner and Hansen in EUROGRAPHICS 2006 presented a paper, “Toward the Light Field Display: Autostereoscopic Rendering via a Cluster of Projectors”, which is hereby incorporated by reference in its entirety. In the paper, the authors describe projecting imagery from an array of projectors onto the diffusing surface of a screen comprising a lenslet array and a diffusing surface separated by the focal length of the lenslets. The diffusing screen serves as an image relay to the back focal planes of the lenslets which then project a light field in the form of an array of pinhole projections.
In US Patent Application US 2014/0063077, “Tensor Displays”, by Wetzstein et al., which is hereby incorporated by reference in its entirety, a 3D display is described that involves a stack of spatially-addressable light attenuating layers. Wetzstein et al also described a “Compressive Light Field Projector” that employs a highly structured lenticular screen and a spatial light modulator. The present technology employs one or more spatial phase modulators and one or more non-conventional optical elements as described herein.
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention. Sizes of various depicted elements are not necessarily drawn to scale and these various elements may be arbitrarily enlarged to improve legibility.